This invention relates generally to a system and method for applying a substantially uniform surface coating to an interior surface of a device, such as the inner diameter surface of a syringe barrel. More particularly, this invention relates to an improved system and method for lubricating the interior of a syringe barrel with a thin and substantially uniformly dispersed coating of a selected lubricant.
Medical syringes are widely used for containing and administering a selected medication to a patient. A typical syringe comprises a generally cylindrical syringe barrel having an open rear end for slide-fit reception of a piston plunger, and an open front or nose end which includes a luer fitting adapted for connection to a hypodermic needle, catheter tube, etc. Retraction of the piston plunger within the syringe barrel is effective to draw liquid such as medication or patient body fluid into the syringe barrel, whereas advancement of the piston plunger delivers liquid from the syringe barrel through the open front luer end thereof. Modern medical syringes of this general type are commonly manufactured predominantly from lightweight molded plastic suitable for disposal after a single use.
In many applications, it is desirable to prelubricate the inner diameter surface of the syringe barrel in order to reduce sliding friction forces as the piston plunger is advanced or retracted. Such reduction of friction forces is especially desirable in syringes designed for use in a programmable medication infusion pump having a battery operated and relatively low power drive means for displacing the piston plunger to administer medication to a patient. Examples of such medication infusion pumps include those available from MiniMed Technologies of Sylmar, Calif. under Model Nos. 504 and 506. See also U.S. Pat. Nos. 4,562,751; 4,678,408, and 4,685,903.
In the past, syringe barrel lubrication has been accomplished by manually placing one or more drops of a selected nontoxic lubricant in liquid form into open rear end of the syringe barrel, and thereafter inserting and stroking the piston plunger with a twisting motion to distribute the lubricant over the inner diameter surface of the barrel. This technique, however, is manual labor intensive and inherently results in at least some scrubbing contact between a piston plunger seal and dry barrel surfaces prior to significant distribution of the lubricant. This scrubbing piston seal-barrel contact often results in chafing of the seal material or rubbing off of prelubricated or preconditioned seal surface treatment onto dry barrel surfaces, thereby reducing the intended effect of such seal surface treatments.
Alternative attempts to lubricate a syringe barrel have involved spraying a liquid-based barrel lubricant into the open rear end of the syringe barrel prior to assembly with the syringe plunger. These attempts have unfortunately resulted in substantially nonuniform application of the barrel lubricant, typically with the lubricant concentrated within the forward or luer end region of the barrel. Subsequent assembly of the syringe plunger with the barrel has still resulted in nonuniform lubrication dispersal and/or rubbing of seal surface treatments onto dry barrel surfaces at the open rear end of the syringe barrel upon initial contact with the piston plunger.
There exists, therefore, a significant need for improvements in apparatus and method for lubricating internal surfaces of a syringe barrel or similar device, particularly wherein a substantially uniform surface coating of lubricant is applied to the syringe barrel prior to barrel assembly with a piston plunger. The present invention fulfills these needs and provides further related advantages.